Heating assembly for domestic forced air electric furnace

ABSTRACT

A heating element assembly which includes a mounting base, a support rack fixed to the mounting base, a plurality of insulators fixed along the lengths of the support rod, and a thin, flat strip of apertured, foil-like electrical resistance material trained through the slots in the insulators. The slots are arranged so that the strip forms a serpentine pattern between endmost insulators and forms flat reaches substantially parallel to each other and to the support rod. The heating element is mounted in a forced air confining duct so that the plane of the resistance material is parallel to the direction of the air flow.

United States Patent [191 Maake 1 1 HEATING ASSEMBLY FOR DOMESTIC FORCED AIR ELECTRIC FURNACE [75] Inventor: Douglas Herman Maake,

Cookeville, Tenn.

[73] Assignee: Gould Inc., Chicago, Ill.

[22] Filed: Dec. 21, 1973 [21] Appl. No.: 427,079

[52] US. Cl. 219/370; 219/375; 219/381; 219/532; 219/546; 338/208; 338/280; 338/321 [51] Int. Cl. H05b 3/02; F24h 3/04; I-IOlc 3/00 [58] Field of Search 219/374-376, 219/381, 382, 369, 370, 532, 536, 537, 542,

1 Aug. 5, 1975 Primary ExaminerA. Bartis Attorney, Agent, or FirmEdward E. Sachs 5 7 ABSTRACT A heating element assembly which includes a mounting base, a support rack fixed to the mounting base, a plurality of insulators fixed along the lengths of the support rod, and a thin, flat strip of apertured, foil-like electrical resistance material trained through the slots in the insulators. The slots are arranged so that the strip forms a serpentine pattern between endmost insulators and forms flat reaches substantially parallel to each other and to the support rod. The heating ele- [56] References Cited t t d f d I f d t th UNITED STATES PATENTS men 18 moun e m orce air con mmg uc so at the plane of the resistance material 18 parallel to the 1,413,001 4/1922 Brooks 338/280 direction of the 1,419,309 6/1922 Russellm. 338/290 X 1,719,872 7/1929 Calcott 219/376 12 Claims, 5 Drawing Figures HEATING ASSEMBLY FOR DOMESTIC FORCED AIR ELECTRIC FURNACE BACKGROUND OF THE INVENTION This invention relates to heating element assemblies and, more particularly, to heating element assemblies which are particularly suitable for domestic forced air electric furnaces. Prior art heating element assemblies include the use of thin, flat strips of apertured, foil-like electrical resistance material as the heating element, and a variety of procedures have been proposed to mount the foil in an immobilized condition relative to glass or ceramic insulators. Metal clips were provided to immobilize the foil in this manner. However, the metal clips require excessive amounts of labor to assemble, since the assembly operation is done by hand. Other arrangements for immobilizing electrical resistance foil involve skewering the foil in a serpentine pattern on glass tubing. This arrangement is not entirely satisfactory, since the glass tubing is too fragile to survive shipping requirements.

The prior art heating assemblies were designed to be installed in a duct, with the plane of the foil substantially perpendicular to the direction of air flow and, in many instances, a plurality of such heating elements were provided in face-to-face apposition with the planes of the faces perpendicular to the flow of air. With such an arrangement, however, the amount of natural convection is reduced and the still air operating temperature of the heating element is increased. Furthermore, downstream heating elements are inefficiently operated, since they tend to pick up heat which is swept from the upstream elements. Since the elements tend to block air flow, increased power is required to move the air through the elements.

SUMMARY OF THE INVENTION This invention overcomes the foregoing prior art problems by providing an electric heating element arrangement which is easy to assemble, rugged enough to survive shipping requirements, and which has its elements oriented parallel to the direction of air flow through the duct so that natural convection is increased while the still air operating temperature of the heating element is reduced. By providing the elements in faceto-face apposition, and in alignment with the air flow, a minimum amount of restriction is presented to the air flow without reduction in heat exchange. As a result, less energy is required to force the air through the heating elements.

According to this invention, a heating element assembly includes a mounting base, a support rod fixed to and projecting from the mounting base, and a plurality of insulators carried by the support rod at spaced locations along its length. Slots are provided at spaced locations in each insulator, and a thin, flat strip of apertured, foil-like electrical resistance material is trained through these slots in a serpentine pattern to form a plurality of flat reaches substantially parallel to each other and to the support rod.

The heating element assembly also includes a U- shaped bracket having legs parallel to the support rod and fixed at their ends to the mounting base. Cross members connect the legs at spaced locations and retain the resistance material within the slots.

The mounting base is constructed so that it permits installation of the unit within the duct of a furnace so that the plane of the flat strip of electrical resistance material is oriented in the direction of air flow.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a heating element assembly according to this invention;

FIG. 2 is an elevational view of the heating element assembly;

FIG. 3 is a fragmentary, perspective view of one of the insulators employed to support the electrical resistance material;

FIG. 4 is a cross sectional view of the heating element showing the direction of the air currents relative to the plane of the element; and

FIG. 5 is a schematic, cross sectional view of a furnace having a heating element assembly mounted therein according to this invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, there is illustrated a heating element support assembly 10. The support assembly 10 includes a support rod 11 having an angularly related leg 12 welded to a mounting base 13. There is provided a plurality of identical insulators carried by the support rod 11 at spaced locations along its length, and including endmost insulators l4 and intermediate insulators 15. As may be seen most clearly in FIG. 3, an intermediate insulator 15 may be fabricated from a suitable ceramic insulating material, and each insulator is provided with a plurality of parallel slots 16 extending into the insulator from one edge thereof. The opposite edge of the IIlSl lator is provided with a notch 32, which straddles the support rod 11.

In order to immobilize the insulator 15 relative to the support rod 11, the first and second insulator abutment means are provided which respectively comprise rods 18 and 19. The rods 18 and 19 are welded to opposite edges of the support rod, and each rod 19 is received within a groove 20 in its insulator. The insulators 15 are biased against their rods by spring clips 21 welded to the support rod and which are flexed to their illustrated positions when the insulators are slipped over the support rod 11 and between the rods 18 and 19. The insulators 15 are thereby locked against retraction, since any effort to withdraw the insulators 15 would tend to cause the spring clips 21 to more firmly bear against the insulator. The endmost insulators 14 are not retained by spring clips but are biased against their rods 18 and 19 in a manner which will hereinafter become apparent.

After the insulators are mounted on the support rod 11 in the previously described manner, a thin, flat strip of apertured, foil-like electrical resistance material 17 is trained through the slots 16 in a serpentine pattern between the endmost insulators 14 to form a plurality of flat reaches substantially parallel to each other and to the support rod 11. The electrical resistance material 17 is more fully described in US. Pat. No. 3,651,304, the disclosure of which is incorporated herein by reference. Since the resistance material 17 has portions 20 wrapped around the surface of the endmost insulators 14, the endmost insulators 14 are biased against the rods 18 and 19, and the insulators 14 are thereby held in place.

The resistance material 17 has ends 21 which are connected to terminal assemblies 22, and the material 17 is held inplace within the slots 16 by a retainer assembly 23. The retainer assembly 23 comprises a U- shaped bracket 24 having legs 25 and 26 parallel to the support rod 11 and fixed at their ends to the mounting base 13. The base of the bracket 24 is connected to the support rod 11 by a rod 30. Cross members 31 connect the legs of the bracket and retain the resistance material 17 within its slots. To prevent shorting of the resistance material, the cross members are coated with a suitable ceramic insulating material.

As may be seen in FIG. 5, the assembly is mounted within a forced air duct so that the resistance material 17 is parallel to the flow of air in the duct. This minimizes the amount of energy required to drive the air through the duct, and also tends to minimize any turbulence within the duct (although as may be seen in FIG. 4, there may be minor local turbulence adjacent the surface of the element 17).

While there have been described what are at present considered to be the preferred embodiments and aspects of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is intended, therefore, in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A heating element support assembly comprising:

a. a mounting base;

b. support rod means fixed to and projecting from said mounting base;

c. a plurality of insulators, including endmost insulators carried by said support rod means at spaced locations along its length and having end portions projecting laterally from said support rod means so that said support rod means is substantially centrally located with respect to said insulators;

d. connecting means between said support rod means and each insulator preventing axial and rotational movement of each insulator relative to said support rod means;

e. a plurality of substantially parallel slots in said laterally projecting portions of each insulator; and

f. a thin, flat strip of apertured, foil-like, electrical re sistance material trained through said slots in a serpentine pattern between the endmost insulators and forming a plurality of flat reaches substantially parallel to each other and to said support rod means.

2. A heating element support assembly according to claim 1, wherein said plurality of insulators includes at least one intermediate insulator between said endmost insulators.

3. A heating element support assembly according to claim 2, wherein said connecting means for each of said insulators comprises a notch in each insulator which receives said support rod means, first insulator abutment means fixed to one edge of said support rod means and contacting one face of its insulator, second insulator abutment means fixed to an opposite edge of said support rod means and contacting an opposite face of said insulator, said endmost insulators being biased against their abutment means by said resistance material, and means biasing each intermediate insulator against its abutment means.

4. A heating element support according to claim 3, wherein the biasing means for each intermediate insulator comprises a spring clip fixed at one end to'said opposite edge of said support rod means and having an opposite end biased against said one face of said insulator.

5. A heating element support according to claim 1, including electrically insulated means extending across the edges of said resistance material and holding said resistance material in said slots.

6. A heating element support assembly comprising:

a. a mounting base;

b. support rod means fixed to and projecting from said mounting base;

0. a plurality of insulators, including endmost insulators carried by said support rod means at spaced locations along its length;

d. connecting means between said support rod means and each insulator preventing axial and rotational movement of each insulator relative to said support rod means;

e. a plurality of substantially parallel slots in each insulator;

f. a thin, flat strip of apertured, foil-like electrical resistance material trained through said slots in a serpentine pattern between endmost insulators and forming a plurality of flat reaches substantially parallel to each other and to said support rod means;

g. a U-shaped bracket having legs parallel to said support rod means and fixed at their ends to said mounting base; and

h. at least one electrically insulated cross member connecting said legs and retaining said resistance material within said slots.

7. A heating element support assembly according to claim 6, wherein said plurality of insulators includes at least one intermediate insulator between said endmost insulators.

8. A heating element support assembly according to claim 7, wherein said connecting means for each of said insulators comprises a notch in each insulator which receives said support rod means, first insulator abutment means fixed to one edge of said support rod means and contacting one face of its insulator, second insulator abutment means fixed to an opposite edge of said support rod means and contacting an opposite face of said insulator, said endmost insulators being biased against their abutment means by said resistance material, and means biasing each intermediate insulator against its abutment means.

9. A heating element support according to claim 8, wherein the biasing means for each intermediate insulator comprises a spring clip fixed at one end to said opposite edge of said support rod means and having an opposite end biased against said one face of said insulator.

10. A heating assembly comprising a duct, blower means attached to said duct for moving air in a path within said duct, a heating element support assembly within said duct comprising a mounting base fixed to said duct, support rod means fixed to and projecting from said mounting base, a plurality of insulators including endmost insulators carried by said support rod means at spaced locations along its length and having end portions projecting laterally from said support rod means so that said support rod means is substantially centrally located with respect to said insulators, connecting means between said support rod means and each insulator, preventin'g a xial and rotational movement of each insulator relative to said support rod means, a plurality of substantially parallel slots in said laterally projecting portions of each insulator, a thin, flat strip of apertured, foil-like electrical resistance material trained through said slots in a serpentine pattern between the endmost insulators and forming a plurality of flat reaches substantially parallel to each other and to said support rod means and substantially parallel to the direction of air flow through said duct means.

11. A heating element support assembly comprising:

a. a mounting base;

b. support rod means fixed to and projecting from said mounting base;

c. a plurality of insulators, including endmost insulators and at least one intermediate insulator between said endmost insulators carried by said support rod means at spaced locations along its length;

d. connecting means between said support rod means and each insulator preventing axial and rotational movement of each insulator relative to said support rod means, said connecting means comprising a notch in each insulator which receives said support rod means, first insulator abutment means fixed to one edge of said support rod means and contacting 6 one face of its insulator, second insulator abutment means fixed to an opposite edge of said support rod means and contacting an opposite face of said insulator, means biasing each intermediate insulator against its abutment means;

e. a plurality of substantially parallel slots in each inwherein the biasing means for each intermediate insulator comprises a spring clip fixed at one end to said opposite edge of said support rod means and having an opposite end biased against said one face of said insulator. 

1. A heating element support assembly comprising: a. a mounting base; b. support rod means fixed to and projecting from said mounting base; c. a plurality of insulators, including endmost insulators carried by said support rod means at spaced locations along its length and having end portions projecting laterally from said support rod means so that said support rod means is substantially centrally located with respect to said insulators; d. connecting means between said support rod means and each insulator preventing axial and rotational movement of each insulator relative to said support rod means; e. a plurality of substantially parallel slots in said laterally projecting portions of each insulator; and f. a thin, flat strip of apertured, foil-like, electrical resistance material trained through said slots in a serpentine pattern between the endmost insulators and forming a plurality of flat reaches substantially parallel to each other and to said support rod means.
 2. A heating element support assembly according to claim 1, wherein said plurality of insulators includes at least one intermediate insulator between said endmost insulators.
 3. A heating element support assembly according to claim 2, wherein said connecting means for each of said insulators comprises a notch in each insulator which receives said support rod means, first insulator abutment means fixed to one edge of said support rod means and contacting one face of its insulator, second insulator abutment means fixed to an opposite edge of said support rod means and contacting an opposite face of said insulator, said endmost insulators being biased against their abutment means by said resistance material, and means biasing each intermediate insulator against its abutment means.
 4. A heating element support according to claim 3, wherein the biasing means for each intermediate insulator comprises a spring clip fixed at one end to said opposite edge of said support rod means and having an opposite end biased against said one face of said insulator.
 5. A heating element support according to claim 1, including electrically insulated means extending across the edges of said resistance material and holding said resistance material in said slots.
 6. A heating element support assembly comprising: a. a mounting base; b. support rod means fixed to and projecting from said mounting base; c. a plurality of insulators, including endmost insulators carried by said support rod means at spaced locations along its length; d. connecting means between said support rod means and each insulator preventing axial and roTational movement of each insulator relative to said support rod means; e. a plurality of substantially parallel slots in each insulator; f. a thin, flat strip of apertured, foil-like electrical resistance material trained through said slots in a serpentine pattern between endmost insulators and forming a plurality of flat reaches substantially parallel to each other and to said support rod means; g. a U-shaped bracket having legs parallel to said support rod means and fixed at their ends to said mounting base; and h. at least one electrically insulated cross member connecting said legs and retaining said resistance material within said slots.
 7. A heating element support assembly according to claim 6, wherein said plurality of insulators includes at least one intermediate insulator between said endmost insulators.
 8. A heating element support assembly according to claim 7, wherein said connecting means for each of said insulators comprises a notch in each insulator which receives said support rod means, first insulator abutment means fixed to one edge of said support rod means and contacting one face of its insulator, second insulator abutment means fixed to an opposite edge of said support rod means and contacting an opposite face of said insulator, said endmost insulators being biased against their abutment means by said resistance material, and means biasing each intermediate insulator against its abutment means.
 9. A heating element support according to claim 8, wherein the biasing means for each intermediate insulator comprises a spring clip fixed at one end to said opposite edge of said support rod means and having an opposite end biased against said one face of said insulator.
 10. A heating assembly comprising a duct, blower means attached to said duct for moving air in a path within said duct, a heating element support assembly within said duct comprising a mounting base fixed to said duct, support rod means fixed to and projecting from said mounting base, a plurality of insulators including endmost insulators carried by said support rod means at spaced locations along its length and having end portions projecting laterally from said support rod means so that said support rod means is substantially centrally located with respect to said insulators, connecting means between said support rod means and each insulator, preventing axial and rotational movement of each insulator relative to said support rod means, a plurality of substantially parallel slots in said laterally projecting portions of each insulator, a thin, flat strip of apertured, foil-like electrical resistance material trained through said slots in a serpentine pattern between the endmost insulators and forming a plurality of flat reaches substantially parallel to each other and to said support rod means and substantially parallel to the direction of air flow through said duct means.
 11. A heating element support assembly comprising: a. a mounting base; b. support rod means fixed to and projecting from said mounting base; c. a plurality of insulators, including endmost insulators and at least one intermediate insulator between said endmost insulators carried by said support rod means at spaced locations along its length; d. connecting means between said support rod means and each insulator preventing axial and rotational movement of each insulator relative to said support rod means, said connecting means comprising a notch in each insulator which receives said support rod means, first insulator abutment means fixed to one edge of said support rod means and contacting one face of its insulator, second insulator abutment means fixed to an opposite edge of said support rod means and contacting an opposite face of said insulator, means biasing each intermediate insulator against its abutment means; e. a plurality of substantially parallel slots in each insulator; and f. a thin, flat strip of apertured, foil-like, electrical resistance mAterial trained through said slots in a serpentine pattern between the endmost insulators and forming a plurality of flat reaches substantially parallel to each other and to said support rod means, said endmost insulators being biased against their abutment means by said resistance material.
 12. A heating element support according to claim 11, wherein the biasing means for each intermediate insulator comprises a spring clip fixed at one end to said opposite edge of said support rod means and having an opposite end biased against said one face of said insulator. 